1. Field of the Invention
The present invention relates to a hydraulic booster adapted to be used in vehicle brakes and the like. More particularly, the present invention pertains to hydraulic brake boosters having electrically operated booster pumps.
2. Description of Prior Art
A hydraulic booster having an electrically operated booster pump has been known for example by U.S. Pat. No. 4,475,336. The known booster is designed so that the pump is driven throughout the operation of the booster to draw hydraulic oil from the reservoir and discharge the oil under pressure into the power chamber of the booster. This arrangement is disadvantageous in that the electrically operated pump is subjected always to a load corresponding to the load on the booster as long as the booster is in operation, so that substantial electric power is consumed and deterioration of oil is increased.